MT040-R Red Battery Isolator Switch The MT040-R is the red-finish version of the MT040 master switch. Mechanics and installers often want the kill switch to stand out on a dark dash or inside a black battery box, and a red cover does exactly that — the unit is spotted immediately when someone needs to cut power in a hurry. The electrical package underneath is unchanged from the standard model. Operation is a straight two-position rotary: turn to ON to close the circuit, turn